Preparation of magnetic polyacrylamide hydrogel with chitosan for immobilization of glutamate decarboxylase to produce γ-aminobutyric acid.

Gamma-aminobutyric acid (GABA) is an vital neurotransmitter, and the reaction to obtain GABA through biocatalysis requires coenzymes, which are therefore limited in the production of GABA. In this study, polyacrylamide hydrogels doped with chitosan and waste toner were synthesized for glutamate decarboxylase (GAD) and coenzyme co-immobilization to realize the production of GABA and the recovery of coenzymes. Enzymatic properties of immobilized GAD were discussed. The immobilized enzymes have significantly improved pH and temperature tolerance compared to free enzymes. In terms of reusability, after 10 repeated reuses of the immobilized GAD, the residual enzyme activity of immobilized GAD still retains 100% of the initial enzyme activity, and the immobilized coenzyme can also be kept at about 32%, with better stability and reusability. And under the control of no exogenous pH, immobilized GAD showed good performance in producing GABA. Therefore, in many ways, the new composite hydrogel provides another way for the utilization of waste toner and promises the possibility of industrial production of GABA.

Waste toner-derived porous iron oxide pigments with enhanced catalytic degradation property.

'Wealth from Waste' is an emerging concept, since it leads an effective waste treatment and waste recyclability. On the other hand, cost effective production iron oxide (IO) nanomaterials is still needed to develop, owing to their wide applications. Herein, we proposed a simple direct calcination method to prepare porous IO (Fe3O4 and Fe2O3) nanomaterials from waste toner powder. Characterization techniques reveal that a structural change happened from Fe3O4 to γ-Fe2O3 and γ-Fe2O3 to α-Fe2O3 at the calcination temperature of 500 °C and 700 °C respectively. Consequently, optical (band gap) and magnetic parameters of IO samples were significantly varied. The pigment characteristics of the IO samples were evaluated using Commission Internationale de l'Eclairage (CIE) analysis. IO900 sample has shown good brown-red coloration (L* = 43.11, a* = 13.26 and b* = 5.69) and it also exhibited good stability in acidic and basic conditions. Practical applicability of IO pigments were also tested by mixing with plaster of paris (PP) powder. Further, porous IO samples were also used as catalysts in the reductive degradation of methyl orange (MO) dye in presence of excess sodium borohydride (NaBH4). IO, prepared at 900 °C exhibited ∼99.9% reduction efficiency within 40 min. Recycling experiments indicated that IO900 possess good stability up to seven cycles. The present porous IO samples will become potential in pigment and environmental remediation.

Influence of Waste Toner on Asphalt Binder: Chemical and Rheological Characterization.

The growing amount of waste toner (WT) has posed a significant environmental challenge. Meanwhile, researchers are interested in the feasibility of utilizing waste toner as an asphalt binder modifier because its primary chemical components (Styrene-acrylic copolymer and carbon black) are known to improve asphalt properties. The objective of this study was to evaluate the chemical and rheological properties of the waste-toner-modified asphalt binder and hence determine the suitability of integrating waste toner for asphalt modification. The waste-toner-modified asphalt (TMA) binders were produced by blending base asphalt with two types of waste toners of different gradation sizes. Microscopic tests such as x-ray fluorescence (XRF), attenuated total reflectance transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy with energy dispersive X-ray (SEM-EDS) and fluorescence microscope, as well as rheology tests such as multiple stress creep recovery (MSCR) tests, oscillation tests, and bending beam rheometer tests were performed. The FTIR results showed that there was a chemical reaction between waste toners and base asphalt binder. A fluorescence effect was observed on the binders produced with different toners used in this research. The binder modified with an optimal content of 8%WTs revealed better high and low-temperature properties. Additionally, 8%WTs used in this research could change the PG70-22 binder to PG76-22 binder. The rutting properties of asphalt material were improved for its improved elasticity. In addition, the 200-mesh TMA binders were desirable with respect to waste toner particle size. Overall, there is a benefit to using waste toner in the asphalt industry.

A field investigation into the characteristics and formation mechanisms of particles during the operation of laser printers and photocopiers.

Indoor particle release from toner printing equipment (TPE) is a major health concern and has received wide attention. In this study, nine printing centers were randomly selected and three working phases were simulated, namely, non-working, normal printing/copying, and heavy printing/copying. The dynamics of the ozone (O3), volatile organic compound (VOC), and particle emissions from TPE were determined by portable detectors. Results showed that particles, VOCs, and O3 were indeed discharged, and particles and VOCs concentrations remained at high levels. Among them, 44% of the rooms represented high-level particle releases. Submicrometer-sized particles, especially nanoparticles, were positively correlated with VOCs, but were inversely proportional to the O3 concentration. Four elements, Ca, Al, Mg and Ni, were usually present in nanoparticles because of the discharge of paper. Si, Al, K, Ni and Pb were found in the submicrometer-sized particles and were consistent with the toner composition. The potential particle precursors were identified, which suggested that styrene was the most likely secondary organic aerosol (SOA) precursor. Overall, the use of the toner formulation and the discharge of paper attribute to the TPE-emitted particles, in which styrene is a specific monitoring indicator for the formation of SOA.

Waste toner-derived micro-materials as low-cost magnetic solid-phase extraction adsorbent for the analysis of trace Pb in environmental and biological samples.

Lead (Pb) is a toxic heavy metal and is commonly used in industrial applications. Thus, Pb poisoning is a concerning public health issue worldwide. The amounts of lead in natural water, urine, and blood can serve as significant indicators for monitoring the exposure of Pb poisoning. Waste toner has the characteristics of both "waste" and "resource," as it is a "resource in the wrong place." Here, a low-cost carboxylate-functionalized magnetic adsorbent was first synthesized from waste toner by a simple thermal treatment and served as a novel adsorbent with a flexible multidentate O-donor for pre-concentration of trace Pb. The characterization, adsorption behavior, and various factors of adsorption and desorption were adequately optimized, and prior to graphite furnace atomic absorption spectrometry (GFAAS) detection, a new magnetic solid-phase extraction method was proposed for the analysis of Pb in real environmental water and biological samples. The developed method exhibited a low detection limit (0.003 µg L-1), high enrichment factor (88.6-fold), good linearity (0.01-0.3 µg L-1), satisfactory precision with relative standard deviations of 7.9% (n = 7, CPb = 0.02 µg L-1), fast adsorption kinetics (5 min), and strong ability to overcome matrix interference. Validation was also performed by analyzing a certified standard reference material, and the method was successfully applied to real tap water, lake water, human urine, and human blood serum with satisfactory recoveries of 92.6-109%.

Versatile and Easily Designable Polyester-Laser Toner Interfaces for Site-Oriented Adsorption of Antibodies.

Laser toners appear as attractive materials for barriers and easily laminated interphases for Lab-on-a-Foil microfluidics, due to the excellent adhesion to paper and various membranes or foils. This work shows for the first time a comprehensive study on the adsorption of antibodies on toner-covered poly(ethylene terephthalate) (PET@toner) substrates, together with assessment of such platforms in rapid prototyping of disposable microdevices and microarrays for immunodiagnostics. In the framework of presented research, the surface properties and antibody binding capacity of PET substrates with varying levels of toner coverage (0-100%) were characterized in detail. It was proven that polystyrene-acrylate copolymer-based toner offers higher antibody adsorption efficiency compared with unmodified polystyrene and PET as well as faster adsorption kinetics. Comparative studies of the influence of pH on the effectiveness of antibodies immobilization as well as measurements of surface ζ-potential of PET, toner, and polystyrene confirmed the dominant role of hydrophobic interactions in adsorption mechanism. The applicability of PET@toner substrates as removable masks for protection of foil against permanent hydrophilization was also shown. It opens up the possibility of precise tuning of wettability and antibody binding capacity. Therefore, PET@toner foils are presented as useful platforms in the construction of immunoarrays or components of microfluidic systems.

Effects of toner-handling work on respiratory function, chest X-ray findings, and biomarkers of inflammation, allergy, and oxidative stress: a 10-year prospective Japanese cohort study.

BACKGROUND: Exposure to toner, a substance used in photocopiers and printers, has been associated with siderosilicosis and other adverse effects. However, these findings are limited, and there is insufficient evidence on the long-term effects of toner exposure. Using longitudinal analysis, this study aimed to examine the effects of work involving toner exposure on the respiratory system over time. METHODS: We conducted a prospective cohort study in a Japanese toner and copier manufacturing enterprise between 2003 and 2013. The cohort included a total of 1468 workers, which comprised 887 toner-handling workers and 581 non-toner-handling workers. We subdivided the toner-handling workers into two groups according to the toner exposure concentration, based on the baseline survey in 2003. We compared the chest X-ray results, respiratory function indicators, and serum and urinary biomarkers of inflammation, allergy, and oxidative stress among the three groups: high-concentration toner exposure group, low-concentration toner exposure group, and non-toner-handling group. To consider the effects of individual differences on the longitudinal data, we used a linear mixed model. RESULTS: Similar chest X-ray results, the biomarkers, and most of the respiratory function indicators were found in the non-toner-handling and toner-handling groups. There were no significant yearly changes in the percentage of vital capacity (%VC) in the high-concentration toner exposure group, while there was a significant yearly increase in %VC in the low-concentration toner exposure group and non-toner-handling group. The yearly change in each group was as follows: high-concentration toner exposure group, - 0.11% (95% confidence interval [CI], - 0.29 to 0.08; P = 0.250); low-concentration toner exposure group, 0.13% (95% CI, 0.09-0.17; P < 0.001); and non-toner-handling group, 0.15% (95% CI, 0.01-0.20; P < 0.001). CONCLUSIONS: In our 10-year prospective study, toner-handling work was not associated with the deterioration of respiratory function and an increase in biomarker values for inflammation, allergy, and oxidative stress. This finding suggests that toner-handling work is irrelevant to the onset of respiratory disease and has minimal adverse effects on the respiratory system under a well-managed work environment.

Unusual pneumoconiosis in two patients with heavy print toner, and paper dust exposure.

Workers in a print shop are exposed to photocopier toner dust and paper dust over a prolonged period of time. However, there are only rare case reports of toner and paper dust induced lung damage in humans. We reviewed our consultation files for a period of 30 years from 1987 to 2018 to look for cases with a diagnosis of giant cell interstitial pneumonia (GIP), printer toner exposure and paper dust exposure resulting in lung disease. There were two cases which met our inclusion criteria. Slides, clinical histories and imaging were reviewed. Both the patients had worked in print shops, and had no history of exposure to hard metals. Patient 1 presented with shortness of breath and cough over several months, while patient 2 was asymptomatic at presentation. Both the patients underwent surgical lung biopsies. Histopathologic examination from both the cases showed a spectrum of pathology, including features of GIP, desquamative interstitial pneumonia, chronic bronchiolitis with lymphoid hyperplasia, and particulate matter consistent with toner. Energy dispersive spectroscopy was performed on one case, and it revealed no cobalt or tungsten particles. The unusual combination of findings is very suggestive that toner particles with or without paper dust exposure were responsible for the pathologic changes in the lungs of these patients. This possibility should be explored further with additional patients who work in print shops where they are exposed to paper dust and paper toner and have signs or symptoms of diffuse lung disease.

Forensic Analysis of Commercial Inks by Laser-Induced Breakdown Spectroscopy (LIBS).

Laser-induced breakdown spectroscopy (LIBS) was tested for all of the relevant issues in forensic examinations of commercial inks, including classification of pen inks on one paper type and on different paper types, determination of the deposition order of layered inks, and analysis of signatures and toners on one questioned document. The scope of this work was to determine the potential of a single LIBS setup that is compatible with portable instruments for different types of ink analysis, rather than building a very large database for inks and papers. We identified up to seven metals characteristic for the examined inks, which allowed to fully discriminate all eight black inks on one type of printing paper. When the inks were tested on ten different papers, the correct classification rates for some of them were reduced for reasons thoroughly studied and explained. The replicated tests on three crossing points, each one involving a pair of blue or black inks, were successful in five cases out of six. In the test simulating documents of forensic interest (questioned documents), LIBS was able to correctly identify the differences in three inks used for signatures on one of the three pages and the use of different printing inks on each page of the document.

Health Effects of Toner Exposure Among Japanese Toner-Handling Workers: A 10-Year Prospective Cohort Study.

The main objective of this study was to evaluate the risk of the respiratory diseases, i.e. pneumoconiosis, lung fibrosis, granulomatous pneumonitis, lung cancer and bronchial asthma, which have been reported as related to toner exposure. The second main objective was to clarify the association between toner exposure and parameters related with toner-handling worker's health. We conducted a 10-year prospective cohort study from 2004 to 2013 in 296 Japanese toner-handling workers. The evaluation of toner exposure and medical health check were performed once a year. There was no obvious evidence of occurrence of lung diseases. We also investigated several health parameters to recognize the change of respiratory health before onset of pneumoconiosis, lung fibrosis, lung cancer and bronchial asthma. However there were some sporadic statistically significant findings, to bring all health parameters, we did not find obvious evidence that toner exposure would cause adverse health effects as a whole. We concluded that the possibility that toner exposure would cause adverse health effects was quite low.

Cytogenetic damage in the buccal cells of photocopying workers in Lahore, Pakistan.

OBJECTIVE: To assess the genotoxic effects associated with workers in relation to the emissions at photocopying centres. METHODS: This case-control study was conducted at the Lahore College for Women University, Lahore, Pakistan, from August to November 2015, and comprised photocopying operators and controls. Micronuclei and other nuclear abnormalities in exfoliated buccal cells were analysed. A structured questionnaire was designed and interviews were conducted face-to-face. Statistical analysis was conducted to evaluate the significance of differences. RESULTS: Of the 200 participants, there were 100(50%) in each group. There were 24(24%) smokers and 76(76%) non-smokers among the controls compared to 29(29%) smokers and 71(71%) non-smokers among the cases. The mean age was 31.08±10.97 years and 28.19±7.58 years in the controls and the cases, respectively. The frequency of deoxyribonucleic acid damage and cell death parameters was high in photocopying operators compared to the controls (p<0.05). Positive correlation was observed between work span and the frequency of deoxyribonucleic acid damage (r=0.226) and cell death parameters (r=0.115). Smoking was positively associated with the frequencies of deoxyribonucleic acid damage (r=0.65) and cell death parameters (r=0.37). The differences were statistically significant (p<0.001). CONCLUSIONS: A highly significant difference was observed in deoxyribonucleic acid damage and cell death of workers associated with photocopy profession.

Results of fibre and toner flotation depending on oleic acid dosage.

The literature was reviewed with respect to deinking flotation methods with toner samples, specifically emphasizing the speciation of copy machine and laser printing, which produce an increasing quantity of paper that is difficult to recycle. Speciation here refers to the physical-chemical characteristics of the toner, which change because of the polymerization (fusion) and oxidation process, due to exposure to heat, light and oxygen (air) during the printing process. To simulate the deinking flotation, after the ideal disintegration process, samples of toner were prepared in order to provide free toner particles. Synthetic toner has iron content and the same physical-chemical features as free disintegrated printed toner particles.We report the toner (I) and fibre (Y) recovery and the brightness (B) of laboratory filter pads formed of deinked product as deinking efficiencies. The application of oleic acid as the collector in the flotation stage gives a better flotation recovery in alkaline than in acidic conditions. The highest brightness (BF = 93.66%) and flotation recoveries (I = 90, Y = 92.82%) were achieved during testing at an oleic acid concentration of 3.38·10(-6) mol l(-1), which is the lowest dose used. This makes the use of oleic acid economical and environmentally friendly.

Antibacterial toner exhibits bactericidal effect against Cutibacterium acnes via keratin and sebum plug penetration.

Cutibacterium acnes is an opportunistic pathogen recognized as a contributing factor to acne vulgaris. The accumulation of keratin and sebum plugs in hair follicles facilitates C. acnes proliferation, leading to inflammatory acne. Although numerous antimicrobial cosmetic products for acne-prone skin are available, their efficacy is commonly evaluated against planktonic cells of C. acnes. Limited research has assessed the antimicrobial effects on microorganisms within keratin and sebum plugs. This study investigates whether an antibacterial toner can penetrate keratin and sebum plugs, exhibiting bactericidal effects against C. acnes. Scanning electron microscopy and next-generation sequencing analysis of the keratin and sebum plug suggest that C. acnes proliferate within the plug, predominantly in a biofilm-like morphology. To clarify the potential bactericidal effect of the antibacterial toner against C. acnes inside keratin and sebum plugs, we immersed the plugs in the toner, stained them with LIVE/DEAD BacLight Bacterial Viability Kit to visualize microorganism viability, and observed them using confocal laser scanning microscopy. Results indicate that most microorganisms in the plugs were killed by the antibacterial toner. To quantitatively evaluate the bactericidal efficacy of the toner against C. acnes within keratin and sebum, we immersed an artificial plug with inoculated C. acnes type strain and an isolate collected from acne-prone skin into the toner and obtained viable cell counts. The number of the type strain and the isolate inside the artificial plug decreased by over 2.2 log and 1.2 log, respectively, showing that the antibacterial toner exhibits bactericidal effects against C. acnes via keratin and sebum plug penetration.

Discrimination and analytical profiling of colored printed documents using ATR-FTIR spectroscopy coupled with explorative and predictive statistical analysis: Part I.

Printed documents are a common form of evidence in forensic document examination. The integration of spectroscopy with chemometrics have evolved evidential analytical interpretation of printing inks. However, we report the first ever study that explores the examination of both black and colored printed documents combined with explorative Principal Component Analysis (PCA) and supervised techniques viz. Soft independent modelling of class analogy (SIMCA) and Partial Least Square- Discriminant Analysis (PLS-DA). The study investigated 74 (40 Ink-based and 34 Toner- based) colored printed document samples using ATR-FTIR to discriminate and determine the source of origin of an unknown printed document using a non-destructive approach. Qualitative analysis by ATR- FTIR indicated the presence of polystyrene, bisphenol A and acrylates as the common binder polymers in the samples. The study was also able to obtain pigment information like presence of PR 57 and PR 146 in magenta, Carbon black in black, Copper Phthalocyanine and PB 15 in Cyan and PY 74 in yellow colored printed samples. Further, PCA has been used as an explorative technique that showed a variance of 97 % in the dataset and indicating that the color Cyan contributes to the maximum classification accuracy. SIMCA has been used as a supervised method to classify the known and test samples to their respective defined classes. However, SIMCA could only classify Toner-based samples in their respective class and inconclusive results were obtained in case of Ink-based samples. Finally, PLS-DA was also used to classify the two class of samples which resulted in a discrimination accuracy of 98.6 %. The derived model was also used for validation study on blind test samples which provided 100 % classification results.

Determining line-crossing sequences between laser printing and black ink using digital microscopy: The influence of writing tool and toner.

One of the recurring issues in forensic document analysis is determining the chronological order of line-crossing sequences. This seemingly simple but tricky task allows forensic laboratories to demonstrate the real order of events. The aim of this work is to analyse black ink/toner intersections using the digital microscope Hirox RH-2000. Five types of pens (ballpoint, gel, rollerball, fountain and fineliner) as well as five different laser printers were used to create the samples. Forensic examiners were tasked with assessing toner fractures, the bronzing effect, and gaps. The findings were analysed to determine the importance of each characteristic for each type of pen. Results indicate that observing the bronzing effect at high magnification (700x) is crucial for establishing the sequence order of application. In this regard, the fineliner pen is considered the most challenging type of pen to analyse in a black ink/toner intersection. The method was validated through a blind test. Based on this, a flow chart has been developed to assist the Forensic Document Examiners (FDEs) in their evaluations. The flow chart emphasises the significance of combining multiple observations and enables a more objective analysis for trained FDEs.

Determining the sequence of intersecting lines formed by laser printer toner and seal ink based on confocal Raman spectroscopy.

In the field of questioned document examination, determining the sequence of intersecting lines is still a technical challenge. This study aims to validate whether confocal Raman spectroscopy can determine the sequence of intersecting lines created by laser prints toner and seal ink through empirical research. The study collected 110 varieties of seal ink and 1074 test pages from 66 models of laser printers available in the Chinese market. Based on the Raman spectral characteristics of the seal ink and the microscopic morphology of the toner, 13 types of seal ink and three types of laser printers were selected for further analysis, producing 78 representative samples of intersecting lines. Confocal Raman spectroscopy was applied to the examination of these samples using a point-scanning mode for enhanced accuracy and efficiency. The experimental results demonstrate that confocal Raman spectroscopy can non-destructively and quickly examine the sequence of intersecting lines produced by laser printer toner and seal ink. Variations in toner forms result in differing levels of difficulty in resolving intersection problems, with the sequence of intersecting lines from toner-dense laser printers being the easiest to ascertain. In contrast, those from printers with porous and dispersed toner present a more significant challenge in examination. This study can be corroborated with other methods proposed, and more significantly, it lays the groundwork for addressing intersection problems related to other printing or writing instruments.

Determination of glyphosate and AMPA on polyester-toner electrophoresis microchip with contactless conductivity detection.

This paper reports a method for rapid, simple, direct, and reproducible determination of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA). The platform described herein uses polyester-toner microchips incorporating capacitively coupled contactless conductivity detection and electrophoresis separation of the analytes. The polyester-toner microchip presented 150 µm-wide and 12 µm-deep microchannels, with injection and separation lengths of 10 and 40 mm long, respectively. The best results were obtained with 320 kHz frequency, 4.5 Vpp excitation voltage, 80 mmol/L CHES/Tris buffer at pH 8.8, injection in -1.0 kV for 7 s, and separation in -1.5 kV. RSD values related to the peak areas for glyphosate and AMPA were 1.5 and 3.3% and 10.1 and 8.6% for intra- and interchip assays, respectively. The detection limits were 45.1 and 70.5 µmol/L, respectively, without any attempt of preconcentration of the analytes. Finally, the method was applied to river water samples in which glyphosate and AMPA (1.0 mmol/L each) were added. The recovery results were 87.4 and 83.7% for glyphosate and AMPA, respectively. The recovery percentages and LOD values obtained here were similar to others reported in the literature.

Encapsulation of Carbon Nanotubes by Styrene and Butyl Acrylate Particles via Suspension Polymerization for Polymerized Toner Applications.

Electrophotographic printing and copying processes primarily use toner, which is a mixture of colorant, polymer, and additives. Toner can be made using traditional mechanical milling techniques or more contemporary chemical polymerization techniques. Suspension polymerization provides spherical particles with less stabilizer adsorption, homogeneous monomers, higher purity, and easier control of the reaction temperature. In contrast to these advantages, however, the particle size resulting from suspension polymerization is too large for toner. To overcome this disadvantage, devices such as high-speed stirrers and homogenizers can be used to reduce the size of the droplets. This research investigated the use of carbon nanotubes (CNTs) instead of carbon black as the pigment in toner development. We succeeded in achieving a good dispersion of four different types of CNT, specifically modified with NH2 and Boron or unmodified with long or short chains in water rather than chloroform, using sodium n-dodecyl sulfate as a stabilizer. We then performed polymerization of the monomers styrene and butyl acrylate in the presence of the different CNT types and found that the best monomer conversion and largest particles (in the micron range) occurred with CNTs modified with boron. The insertion of a charge control agent into the polymerized particles was achieved. Monomer conversion of over 90% was realized with all concentrations of MEP-51, whereas conversion was under 70% with all concentrations of MEC-88. Furthermore, analysis with dynamic light scattering and scanning electron microscopy (SEM) indicated that all polymerized particles were in the micron size range, suggesting that our newly developed toner particles were less harmful and environmentally friendly products than those typically and commercially available. The SEM micrographs clearly showed good dispersion and attachment of the CNTs on the polymerized particles (no CNT aggregation was found), which has never been published before.

Dynamic Light Scattering and Its Application to Control Nanoparticle Aggregation in Colloidal Systems: A Review.

Colloidal systems and their control play an essential role in daily human activities, but several drawbacks lead to an avoidance of their extensive application in some more productive areas. Some roadblocks are a lack of knowledge regarding how to influence and address colloidal forces, as well as a lack of practical devices to understand these systems. This review focuses on applying dynamic light scattering (DLS) as a powerful tool for monitoring and characterizing nanoparticle aggregation dynamics. We started by outlining the core ideas behind DLS and how it may be used to examine colloidal particle size distribution and aggregation dynamics; then, in the last section, we included the options to control aggregation in the chemically processed toner. In addition, we pinpointed knowledge gaps and difficulties that obstruct the use of DLS in real-world situations. Although widely used, DLS has limits when dealing with complicated systems, including combinations of nanoparticles, high concentrations, and non-spherical particles. We discussed these issues and offered possible solutions and the incorporation of supplementary characterization approaches. Finally, we emphasized how critical it is to close the gap between fundamental studies of nanoparticle aggregation and their translation into real-world applications, recognizing challenges in colloidal science.

Evaluation of the cytotoxic and genotoxic potential of printer toner particles in a 3D air-liquid interface, primary cell-based nasal tissue model.

Printer toner particles (TPs) are a common, potentially hazardous substance, with an unclear toxicological impact on the respiratory mucosa. Most of the airways surface is covered by a ciliated respiratory mucosa, therefore appropriate tissue models of the respiratory epithelium with a high in vivo correlation are necessary for in vitro evaluation of airborne pollutants toxicology and the impact on the functional integrity. The aim of this study is the evaluation of TPs toxicology in a human primary cell-based air-liquid-interface (ALI) model of respiratory mucosa. The TPs were analyzed and characterized by scanning electron microscopy, pyrolysis and X-ray fluorescence spectrometry. ALI models of 10 patients were created using the epithelial cells and fibroblasts derived from nasal mucosa samples. TPs were applied to the ALI models via a modified Vitrocell® cloud and submerged in the dosing 0.89 - 892.96 µg/ cm2. Particle exposure and intracellular distribution were evaluated by electron microscopy. The MTT assay and the comet assay were used to investigate cytotoxicity and genotoxicity, respectively. The used TPs showed an average particle size of 3 - 8 µm. Mainly carbon, hydrogen, silicon, nitrogen, tin, benzene and benzene derivates were detected as chemical ingredients. By histomorphology and electron microscopy we observed the development of a highly functional, pseudostratified epithelium with a continuous layer of cilia. Using electron microscopy, TPs could be detected on the cilia surface and also intracellularly. Cytotoxicity was detected from 9 µg/ cm2 and higher, but no genotoxicity after ALI and submerged exposure. The ALI with primary nasal cells represents a highly functional model of the respiratory epithelium in terms of histomorphology and mucociliary differentiation. The toxicological results indicate a weak TP-concentration-dependent cytotoxicity. AVAILABILITY OF DATA AND MATERIALS: The datasets used and analysed during the current study are available from the corresponding author on reasonable request.